János, Tóth F. wrote: > Advanced Startup Options (Metro UI sidebar [top left corner] / Settings / > Change PC Settings / General [scroll down]) > Disable driver signing enforcement > > or > > Start cmd.exe with full Administrator rights > bcdedit.exe /set testsigning on > reboot It seems that testsigning only works for the developer/preview releases of Win 8, and not for the final release, just like Vista & Win 7. So the only reliable way of installing the USB drivers is to reboot in "Disable driver signing enforcement" mode. Once the driver is installed, it will work fine without being in this mode. [The libusb0.sys is signed, but the Disable driver signing enforcement" mode is needed for Win 8 to install the unsigned .inf file.] I'm unifying the .inf file for the next ArgyllCMS release, so the "Disable driver signing enforcement" mode will only be needed once, and not for each different instrument type. In fact after installing the first instrument, subsequent instruments will work straight away. Graeme Gill.